Certain cyclopentenones possessing an endocyclic double bond in the five membered ring and an alkyl substituent in the .alpha.- or .beta.-position with respect to the carbonyl group represent useful raw materials for the synthesis of a variety of products destined to the perfumery and flavour industry, as well as to the pharmaceutical one, namely for the preparation of steroids.
Very numerous processes for their preparation have been described so far. For instance a review for the preparation of 2-methyl-2-cyclopentenone has been recently published by R. L. Funk and K. P. C. Vollhardt [see Synthesis 1980, 118].
For the preparation of other 2-cyclopentenones see also the references cited by F. Naef et al. [Helv. Chim. Acta, 61, 2524 (1978)], T. L. Ho et al. [Chem. Ind. (London) 1982, 371-372] and McCurry et al. [J. Org. Chem. 29, 2317-2319 (1974)].
The known methods are based on multistep uneconomical processes and their industrial exploitation suffer from this major drawback.
The instant invention, which is based on a new straightforward reaction, offers an original solution to this problem, thus enabling the industrial convenient preparation of these useful materials.